Solid end static discharger

ABSTRACT

A solid end static discharger for use with aircraft, the discharger employing a solid resistive rod having pre-determined electrically conductive characteristics and terminating outwardly in a machined end. An electrically conductive ionization bypass may be employed to over-fit portions of the solid rod to shunt extremely high electrical energies to protect against electrical overload.

United States Patent [1 1 Floyd June 26, 1973 [54] SOLID END STATIC DISCHARGER 3,585,447 6/1971 McLain .0 317/2 E [76] Inventor: George M. Floyd, 514 Lansdowne Avenue, Camd N ()8 1 ()4 Primary ExaminerGerald Goldberg Attorne -Karl L. S ivak 221 Filed: Dec. 8, 1971 y p [2]] Appl. No.: 206,047 [57] ABSTRACT I 521 vs. c1 317/2 E 9 iggj if ffig fiz g fii gg Kg-Egg [51 Int. Cl. 864d 45/02, H05f 3/00 d d l n d h, d [58] Field of Search 117/2 R 2 E 5 C actemms terminating outwardly in a machined end. An electri- V cally conductive ionization bypass may be employed to [56] References cled over-fit portions of the solid rod to shunt extremely UMTED STATES PATENTS high electrical energies to protect against electrical 3,633,068 l/l972 Miller 317/2 E overload,

3,034,020 5/1968 Benkoczy et al 3l7/2 E 3,579,033 5/1971 Phillips 317/2 E 3 Claims, 3 Drawing Figures SOLID END STATIC DISCHARGER BACKGROUND OF THE INVENTION The present invention relates generally to the field of static dischargers, and more particularly, is directed to a novel static discharger of the solid resistance rod type which may be employed in conjunction with an external ionization by-pass, for protection against electrical over-load.

This invention is concerned with the removal of static electric charges from aircraft in order to prevent corona discharge in the vicinity of radio antennae inasmuch as it has been found that the corona discharge is a source of electromagnetic interference which can disrupt the normal radio communications in aircraft. In order to minimize these effects and the noise of corona discharge, static discharge devices have been placed at the extremities of the air frame of aircraft by prior workers in the field. In particular, static dischargers are usually affixed at the trailing and lateral edges of the wings and horizontal stabilizers and at the top and trailing lateral edges of the vertical stabilizer. The location and installation of such static dischargers has been set forth in US. Pat. No. 3,558,976 to Miller.

Most prior art static dischargers as presently in use are either of the wick type which employ a length of graphite impregnated cotton enclosed in a plastic tube, the so called null field type which include a high impedance rod having an electrically conductive coating externally affixed thereon and employing a tungsten static discharge pin positioned at right angles to the axis of the rod or are of the internal resistive element type as disclosed in the aforesaid US. Pat. No. 3,558,976. The prior art types of static dischargers function to provide a localized area where static precipitation can be leaked off by corona discharge before the charge buildup is of sufficient magnitude to cause the air frame itself to discharge by corona discharge. Since this corona discharge takes place at the extremities of the aircraft remote from the radio antennae, the affect of the corona noise on the radio communications is thereby minimized.

SUMMARY OF THE INVENTION The present invention includes a solid end static discharger which incorporates a single, monolithic, solid electrically resistive rod for static discharge purposes. The remote end of the rod is milled or otherwise machined to a shaped, cross-section configuration to facilitate static discharge. No discharge needle or additional construction is employed.

The connected end of the rod is threaded and conventionally is provided with a stainless steel contact to threadedly engage and electrically connect to a mounting bracket which affixes to the air frame of an aircraft in an electrically conductive manner as well known in the art. If desired, the resistive rod can be provided with an ionization by-pass which is capable of handling large quantities of electrical energy without wear, deterioration or other indication of mechanical breakdown. A stainless steel sleeve forms the ionization by-pass and the sleeve overfits and affixes to the outer periphery of the resistive rod. In this manner, the sleeve provides a external, electrically conductive by-pass to thereby shunt high energy such as produced by lightning and other conditions in electrical storms without damage to the electrically resistive rod.

The shaped end of the solid rod positions outwardly from the stainless steel sleeve and performs all functions of static discharge which formerly required the tungston needle. The present unit is exceedingly durable and efficient due to this improved design and construction. It is capable of prolonged periods of use under normal operating conditions and is further capable of handling repeated high energy strikes of lightning without any visible or measurable harm or damage.

It is therefore an object of the present invention to provide an improved static discharger of the type set forth.

It is another object of the present invention to provide an improved solid rod static discharger which terminates outwardly in a solid end.

It is another object of the present invention to pro vide an improved solid rod static discharger which terminates outwardly in a solid end which has been milled to a desired cross-sectional configuration.

It is another object of the present invention to provide a novel solid rod static discharger incorporating an ionization by-pass sleeve which is externally affixed to the discharger construction.

It is another object of the present invention to provide a novel static discharger of the solid rod type which terminates outwardly in a solid end which has been milled to a hexagonal cross-sectional configuration.

It is another object of this invention to provide a novel solid rod static discharger that is rugged in construction, inexpensive in manufacture and trouble free when in use.

Other objects and a fuller understanding of the invention will be had by referring to the following description and claims thereof taken in conjunction with the accompanying drawings wherein like reference character have been employed to designate like parts throughout in the several views and in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a solid end static discharger in accordance with the present invention.

FIG. 2 is a side elevational view of the static discharger of FIG. 1, partially broken away to expose details of internal construction.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2, looking in the direction of the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of my invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.

Referring now to the drawings, I show a static discharger 10 which includes a mounting base 12, a resistive element 14, a conductive contact 16 and optionally, an electrically conductive by-pass 18, all of which function as a unit to bleed static electrical charges from the surface of an aircraft (not shown) while in flight.

The mounting base 12 is fabricated of weather resistant, electrically conductive material, such as aluminum, and is secured to the aircraft (not shown) in an electrically conductive permanent manner such as by riveting or by using electrically conductive cement. The base includes a threaded socket 20 which opens rearwardly to threadedly receive the resistive element 14 therein. The forward portion 22 of the base is preferably cast or otherwise formed of solid aluminum or other construction which is in electrical continuity with the base mounting flange 24. Thus static electrical charges which build up on the skin of an aircraft (not shown) are transmitted directly to forward portion 22 of the base'l2 through the base mounting flange 24. The conductive material of the forward portion 22 terminates at the bottom of the threaded socket 20 for electrical connection with the conductive contact 16 as hereinafter more fully set forth.

The resistive element 14 is preferably formed to an elongate cylindrical configuration which terminates forwardly in an externally threaded section 26 and rearwardly in a milled section 28. A conductive contact 16 affixes to the forward end 30 of the resistive element 14 in an electrically conductive manner, such as by employing electrically conductive cement.

The conductive contact 16 comprises a contact point 32 and an integral mounting flange 34. When the threaded section 26 is fully turned into the base threaded socket 20, the contact point 32 is forced into electrically conductive contact with the forward portion 22 of the base 12 to conduct static charges from the aircraft (not shown) to the resistive element 14.

The resistive element 14 has been specifically designed to meet the requirements of MIL-D-9l29B dated Nov. 8, 1967 and the entire unit with by-pass should conform to lightening test as per MIL-C-383- 73A (ASG), sections 4.6.14.2 and 4.6.14.3.

The following table sets forth test data relating to current discharge when employing resistive elements in accordance with the present invention:

Resistive Micro Resistive Resistive Resistive element Amps element element element megohms 5.0

2.0 3.4 5.0 with megohms megohms megohms by-pass I 23.0 KV 24.0 KV 22.0 KV 23.7 KV 2 27.0 KV 29.5 KV 27.0 KV 28.3 KV 4 38.5 KV 37.3 KV 36.8 KV 37.0 KV 7.3 48.5 KV 47.7 KV 47.1 KV 47.3 KV

Prior art static dischargers employing resistive elements, when tested in accordance with MIL-D-2929B, section 4.7.2.2 showed the following noise measurements:

Current Resistive Resistive element Micro-amps element with needle with brush 35 db 45 db 35 db 45 db l5 35 db 45 db 20 38 db 45 db 25 40 db 45 db 30 40 db 45 db 35 4| db 45 db 40 4l db 45 db 45 4l db 45 db 50 39 db 45 db Static dischargers with solid ends, having no needles or brushes, as hereinbefore described, when tested to the same current levels, recorded the following noise measurements:

Current Micro-amps Round Square Triangle Hexagonal End End End End i0 59 db 55 db 58 db 60 db l5 59db 55 db 42db =60db 2O 59 db 50 db 40 db 60 db 25 59 db 50 db 35 db 60 db 3O 59 db 50 db 40 db 60 db 35 59 db 50 db 35 db 60 db 40 59 db 50 db 35 db 60 db 45 57 db 50 db 35 db 60 db 50 55 db 50 db 35 db 6() db Thus it can be readily demonstrated that static dischargers constructed with solid ends in accordance with the present invention exhibit better noise suppressing characteristics in almost every configuration and current level, than the prior art types.

Preferably the resistive element 14 should be composed of an inexpensive epoxy base material specially compounded for the severe condition imposed by its ultimate use with aircraft such as extreme low temperature flexibility, surface toughness, an excellent adhesive and aging characteristics, the ability to be cast to shape and to be machined and the potential to be sprayed and dipped. One material suitable for the purpose is marketed under the trade name Avres-Ca Rods by Avco Corporation, Lowell, Mass.

The ionization by-pass 18 is formed to a hollow cylindrical sleeve having an internal bore 42 which closely overfits and is affixed to the resistive element 14. As best seen in FIG. 2, the by-pass 18 positions upon the resistive element 14 between the milled section 28 and the rearward end 36 of the mounting base 12 and defines a non-conductive gap between the sleeve and the base 12. Preferably, the by-pass is formed of stainless steel or other corrosion resistant, electrically conductive material and is crimped, cemented or otherwise affixed in position about the outer periphery of the resistive element 14. The non-conductive gap 38 serves the purpose of permitting high energies such as may be developed in electrical storms to are across for discharge at the by-pass 18 to thereby minimize the danger of electrical damage to the resistive element 14 itself. During all periods of normal conditions, the gap 38 should be great enough to offer sufficient resistance to the flow of static charges as to force all such static charges to normally travel through the element 14 for discharge at the milled section 28.

Surprisingly, it has been found that the common discharge needle (not shown) that is usually employed at the discharge end of prior art static dischargers can be entirely eliminated by machining the discharge end of a solid element statis discharge without loss of function.

Various cross'sectional configurations have been employed at the milled section 28, such as square, pentag onal, hexagonal, octagonal and the like. As best seen in H68. 1 and 3, a hexagonal configuration 40 has been selected as the most efiicient shape for static discharge purposes without a conventional needle. However, other configurations can give satisfactory results such as round, obround, irregular and the like and are considered to be within the scope of the present invention. The milled or otherwise configured section 28 entirely obviates the need for a metallic needle and permits the static discharger 10 to function satisfactorily under all conditions of use and to meet or exceed all standards of performance which have to date been established by any authority or regulatory body having jurisdiction.

I claim:

1. In a static discharger for discharging static charges from an aircraft of the type employing a conductive base affixed to the aircraft in an electrically conductive connection, the combination of:

A. an electrically resistive, elongate element removably connected to the base; I. said element having a first end and a second end, a. a conductive contact affixed to the first end in an electrically conductive connection, b. said conductive contact contacting the conductive base in an electrically conductive connection,

2. said element being fabricated of a uniform composition throughout, a. said element being solid throughout its length, b. said element having uniform electrical resistive characteristics throughout, c. said element having no internal bore or surface 2. The invention of claim 1 wherein said discharge 10 end terminates outwardly in a flat face, said flat face lying in a plane positioned at right angles to the longitudinal axis of the element.

3. The invention of claim 2 wherein the static discharge end of the element is formed to a cross sectional indentations, 3. the said second end terminating outwardly in a configuration that is regular polygon in shape. 

1. In a static discharger for discharging static charges from an aircraft of the type employing a conductive base affixed to the aircraft in an electrically conductive connection, the combination of: A. an electrically resistive, elongate element removably connected to the base;
 1. said element having a first end and a second end, a. a conductive contact affixed to the first end in an electrically conductive connection, b. said conductive contact contacting the conductive base in an electrically conductive connection,
 2. said element being fabricated of a uniform composition throughout, a. said element being solid throughout its length, b. said element having uniform electrical resistive characteristics throughout, c. said element having no internal bore or surface indentations,
 3. the said second end terminating outwardly in a sTatic discharge end, a. said static discharge end being integral with and being fabricated of the same composition as the elongate element, b. said discharge end being of uniform composition and having no metallic components associated therewith, and
 4. said element having a longitudinal axis.
 2. said element being fabricated of a uniform composition throughout, a. said element being solid throughout its length, b. said element having uniform electrical resistive characteristics throughout, c. said element having no internal bore or surface indentations,
 2. The invention of claim 1 wherein said discharge end terminates outwardly in a flat face, said flat face lying in a plane positioned at right angles to the longitudinal axis of the element.
 3. The invention of claim 2 wherein the static discharge end of the element is formed to a cross sectional configuration that is regular polygon in shape.
 3. the said second end terminating outwardly in a sTatic discharge end, a. said static discharge end being integral with and being fabricated of the same composition as the elongate element, b. said discharge end being of uniform composition and having no metallic components associated therewith, and
 4. said element having a longitudinal axis. 